And a reward is being offered in the case of that missing mother from michigan who vanished while closing up the gas station where she worked. Abc's alex perez has the latest. Reporter: Overnight inch by inch police search the michigan state park for any sign of jessica heeringa, but no luck. The ground search at the park was ordered after someone reported hearing gunshots. It's been a week since heeringa vanished as she was wrapping up her late night shift at this exxon mobil gas station in norton shores. There's no way that she would just leave like that on her own free will. No way. That's not -- that's just not going to happen. Reporter: Police are on the hunt for this man, authorities say this suspect was seen at the gas station in a silver minivan about the time she disappeared last friday night. The station did not have security cameras, but investigators released a second surveillance video from a nearby business showing the silver minivan driving away. They've received more than 500 tips and questioned more than 20 and the search is growing. Thousands of flyers and now a $15,000 reward for any information that could help this heartbroken community get some answers. For "good morning america," alex perez, abc news, chicago.

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